Project Summary Esophageal dysfunction and pathology represent significant health burdens in the United States and worldwide. While patient age is an established risk factor for dysphagia, esophageal cancer and Eosinophilic Esophagitis (EoE)-associated subepithelial fibrosis, our understanding of the biology of aging in the esophagus remains elusive. Under homeostatic conditions, esophageal squamous epithelium comprises a basal compartment of proliferative cells that undergo differentiation in suprabasal layers and luminal desquamation, facilitating tissue renewal. Perturbation of this defined proliferation/differentiation gradient in esophageal epithelium is a feature of esophageal pathologies, including EoE. While the prevalence of BCH is nearly identical in pediatric and adult patients with active EoE, preliminary data indicate that BCH is present in ~20% of normal esophageal epithelial specimens from adults while remaining undetectable in normal pediatric specimens. We have recently demonstrated that autophagy (?self-eating?) is activated in esophageal epithelium in response to EoE inflammation, serving to limit BCH and eosinophilia. Preliminary data indicate that autophagy flux is stalled in aged esophageal epithelium under normal conditions. Moreover, EoE induction in aged mice results in diminished eosinophilia and subepithelial fibrosis. The overarching hypothesis is that age-associated decline in esophageal epithelial autophagy flux impairs tissue homeostasis and contributes to age-associated alterations in EoE phenotype. To test this hypothesis, we will define the functional relationship between mTORC1/autophagy signaling and age-associated esophageal basal cell hyperplasia (Aim 1); elucidate the functional role of epithelial autophagy in age-associated EoE fibrosis (Aim 2); and investigate the role of epithelial autophagy in the EoE inflammatory response in the context of aging (Am 3). The biology of aging in the esophagus represents a significant knowledge gap as understanding mechanisms of tissue aging has the potential to improve strategies for diagnosis, monitoring and therapy of widely prevalent esophageal diseases, including EoE and cancer. Here, we investigate epithelial autophagy as a novel regulator of aging in the esophagus under conditions of homeostasis and EoE inflammation using an innovative approach coupling functional evaluation of human endoscopic biopsies, 3D esophageal organoids and a murine model of EoE featuring age-associated fibrosis. These studies have great potential to provide novel insight into age-relevant mechanisms/cellular phenotypes in the esophagus and unveil new biomarkers and therapeutic targets for EoE and other age-associated disorders affecting the esophagus.